It is a widely distributed and extremely harmful chicken parasitic disease. In poorly managed chicken farms, the morbidity and mortality of chicks are very high, and sometimes the mortality can reach 80%. The growth and development of tolerant chickens are seriously affected and become carriers. After adult chickens are infected with coccidia, most of them will not get sick, but carrying worms will also have a certain impact on the laying and weight gain of chickens. 15 ~ 50-day-old chickens are most susceptible to this disease, and it is most popular in the season when the temperature is 20 ~ 30℃ and there is more rain. The incidence of coccidiosis can reach about 70%, and the mortality rate ranges from 20% to 50%.

The onset age of coccidiosis invading cecum is earlier, and that invading small intestine is later. The incidence of chickens raised on the ground is higher than that raised in cages. Contaminated feed, drinking water, dust, bedding, utensils, insects and feeding managers can spread diseases mechanically; Improper feed mix, such as malnutrition, vitamin A deficiency, vitamin K3 deficiency, poor environmental sanitation, such as wet pens, poor ventilation, poor air quality, high feeding density, population transfer stress, vaccination and other factors, are conducive to the occurrence of coccidiosis, which can aggravate the occurrence of coccidiosis or cause outbreaks.

(2) Pathogenic characteristics

The pathogen of the disease is a variety of Eimeria in Eimeria. Eimeria is characterized by four sporangia in the oocyst, and each sporangia has two sporozoites. At present, there are 9 species of Eimeria that are recognized as parasites in chicken intestines in China, among which Eimeria tenella and Eimeria toxicaria are the most pathogenic, and they are parasitic in chicken cecum and small intestine respectively. These nine different species of Eimeria can be identified according to the size, shape and color of their oocysts, as well as the time of sporulation in the outside world, the time required from the host to swallow the oocysts and expel them from the host's feces, parasitic parts and pathological characteristics.

Coccidiosis is usually excreted in oocysts, which are ovoid, ovoid, round and melon seed-shaped. The basic structure of oocysts includes oocyst wall and protoplasm. Some oocysts have an egg membrane hole at the slightly pointed end, and some inner membranes protrude from the egg membrane hole to form a polar cap. Under suitable external conditions, oocysts reproduce from spores to form sporangia, and sporozoites are formed in the sporangia, so the sporulated oocysts are infectious.

(3) Main symptoms

① Cecal coccidiosis: It first occurred at the age of 7-8 days. At the beginning of the disease, sick chickens excrete foul-smelling feces with undigested feed, and then discharge orange feces or carrot-like bloody feces. Most feces and water are separated, the crown and mucous membrane are anaemic, listless, eyes are closed, wings are drooping, feathers are loose, people are afraid of cold, drowsiness, foot paralysis or spasm, and crop is full of liquid. Died 2 ~ 3 days after onset.

② Coccidiosis of small intestine: It mostly occurs in cage or flat chickens from 3 to 20 weeks old. The sick chickens are characterized by elevated body temperature, gloomy crown, listlessness, loose feathers, necking, standing still or unable to walk, watery crop (some chickens are empty), thin and small feces, or green and white sparse feces, mixed with exfoliated intestinal mucosa. Generally, they die within 2 ~ 3 days after symptoms appear, and all dead chickens are obese. The course of the disease is a little longer, which is characterized by dysplasia, emaciation and anemia, pecking at the tail root, pecking at the anus, twisting the neck, looking back, extending the lower limbs straight forward and paralysis of the legs.

(4) Anatomical lesions

① Cecal coccidiosis: the cecum is extremely thick and purple, with blood and blood clots in the intestinal cavity and mucosal erosion. Systemic muscle anemia, other organs have different degrees of anemia characteristics.

② Small intestinal coccidiosis: the diseased intestine is unusually thick, which is 1 ~ 4 times thicker than normal. Thicker intestinal mucosa and muscularis necrotic and exfoliated, leaving only the outermost serosa layer. Most of these sick chickens are poisoned by themselves. Red and gray spots, red circles and massive bleeding can be seen in the serosa layer. In the middle and late course of the disease, intestinal mucosal edema and hypertrophy or mucosal erosion.

(5) Prevention and control measures

Standardizing feeding management and strengthening disinfection are effective measures to prevent chicken coccidiosis. (1) Spray or spray 20% lime water or 30% plant ash water or Baidusha disinfectant (mixed with water as required) to disinfect pens, tableware and utensils. Maintain proper temperature, humidity and feeding density. ② In the epidemic season of this disease, vitamin A and vitamin K should be given to enhance the body's immunity and improve the antibody level. ③ Chickens can be fed with anticoccidial drugs, such as diclazuril, ampicillin and decoquinate. The best dosage is 3-5 days.

There are many kinds of drugs to prevent and control chicken coccidiosis, so we should consider the drug residue and drug resistance. It is suggested that farmers choose drugs according to the local market and use them alternately. One medicine can be used continuously for 5 ~ 7 days, and then another medicine can be changed in a few days. If the weather is dry and the chickens are healthy, the interval can be appropriately extended. During the prevention and treatment of other diseases in chickens with various antibacterial drugs, it is not necessary to use anticoccidial drugs, because general antibacterial drugs have a good control effect on coccidiosis.